Bubbling fountains on Kinnickinnic River signal help is on the way for fish

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Nick Hayden (left) and Evan Murdock with Montgomery Associated test the dissolved oxygen levels on the Kinnickinnic River just north of the E. Lincoln Ave. bridge in Milwaukee. The Milwaukee Metropolitan Sewage District installed several aerators to mix more oxygen into the river in attempt to boost dissolved oxygen levels in the water for the benefit of fish and other aquatic life. Mike De Sisti / Milwaukee Journal Sentinel

Nick Hayden (left) and Evan Murdock with Montgomery Associated test the dissolved oxygen levels on the Kinnickinnic River just north of the E. Lincoln Ave. bridge in Milwaukee. Mike De Sisti / Milwaukee Journal Sentinel

South side Milwaukee residents will see six bubbling fountains of water on the Kinnickinnic River downstream of Chase Ave. on various days through June of next year as part of an effort to improve conditions for fish to live there.

A contractor for the Milwaukee Metropolitan Sewerage District installed six floating mechanical aerators in the river last week in a first test of how much oxygen they could mix into the water, MMSD senior project manager Courtney Allen said.

At this time, water in a stretch of just under a mile between I-94 and Becher St. does not contain enough dissolved oxygen to sustain fish and other aquatic life, Allen said.

Low oxygen levels in shallow, stagnant water in that stretch have been a recurring problem and act as a barrier to fish attempting to swim upstream from the harbor.

The river is healthier upstream of I-94 and downstream of Becher Ave.

Among the reasons for the poor water quality in the troubled stretch is slow flow on the generally flat bed of the stream there and the presence of bacteria and other microorganisms that use up the oxygen as they digest organic matter in the water and muck. Downstream of Becher Ave., the river is influenced by water pushed into the harbor estuary from Lake Michigan.

"It takes several days for the water to travel between Chase and Becher," said Michael Schwar, consultant project manager for Montgomery Associates Resources Solutions LLC of Cottage Grove. "So the microorganisms have a long time to bring oxygen levels down."

A minimum of 5 milligrams of dissolved oxygen per liter of water is needed to sustain fish and other animals living in the river, Schwar said.

"We are well below that much of the year," he said. The lowest amounts of dissolved oxygen are found in warm weather months between May and September.

Until 2008, the district had used a historic Kinnickinnic River flushing station to pour Lake Michigan water into the stream and give it a quick hit of dissolved oxygen. A tunnel beneath Bay View carried lake water to a riverbank outlet at Chase Ave.

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Nick Hayden (left) and Evan Murdock with Montgomery Associated test the dissolved oxygen levels on the Kinnickinnic River just north of the E. Lincoln Ave. bridge in Milwaukee. The Milwaukee Metropolitan Sewage District installed several aerators to mix more oxygen into the river in attempt to boost dissolved oxygen levels in the water for the benefit of fish and other aquatic life.(Photo: Mike De Sisti / Milwaukee Journal Sentinel)

A 2013 study found that the cost of needed tunnel and pumping station repairs did not justify the temporary benefits of periodic discharges of lake water to the river.

A $850,000 grant from the state Department of Natural Resources is paying costs of the aeration study and proposed construction of in-stream habitat improvements. All work must be completed by September 2018, under terms of the grant.

MMSD hired Montgomery Associates to help the district find a solution.

For the four-day September test, two aerators were suspended from each of three heavy plastic tubes on the south shore of the river. Each aerator is attached to the bottom of a donut-shaped plastic ring with a hole in the center.

A spinning propeller on the bottom of an aerator pulls water up into the ring and pushes it out of the hole to create a bubbling fountain, Schwar said.

Droplets tossed into the air absorb oxygen between water molecules — that is why it is called dissolved oxygen — before dropping back into the river. The turbulence helps stir the much-needed oxygen into the stagnant river.

Two Montgomery Associates employees were in a boat on the river several times last week to test the impact of the aerators. One crew member lowered a digital probe into the water to measure and record dissolved oxygen levels downstream of the aerators.

The aerators might be turned on again for a few days in October if the weather remains unseasonably warm. If not, testing will resume in April 2018 and run through June, Schwar said.